The invention is based on a rotation angle sensor having at least one coil, which is provided with windings, as well as an element which interacts with the coil, is magnetically conductive, and can rotate with a shaft for transmission of the sensed rotary movement.
EP 0 797 078 A1 discloses a rotation angle sensor in which the coil is wound on a coil former, which is in the form of a box and is composed of a non-magnetically permeable material whose side openings are partially covered by sheets composed of magnetically conductive material. The rotatable element is attached as a flag to the shaft and is mounted completely within the coil former in every rotation position. The rotatable element covers or overlaps the side sheets differently, depending on the rotation position. The linear response of the rotation angle sensor is then achieved by the essentially linear relationship of the coverage or overlap area, which is formed between the rotatable element and the sheets. The angular position of the rotatable element is changed by rotation of the shaft, and its coverage area of the sheets is therefore also changed, resulting in a measurable change in the magnetic reluctance of the magnetic circuit, and therefore in the inductance.
Rotation angle sensors of the above generic type are known from DE 42 33 549 A1 and DE 197 45 823 A1.
In contrast, the present invention is based on the object of further developing a rotation angle sensor so as to ensure greater accuracy and better resolution.
According to the invention, this object is achieved by having at least one coil, which is provided with windings, as well as an element which interacts with the coil, is magnetically conductive, and can rotate with a shaft for transmission of the sensed rotary movement. The magnetically conductive element has a different coverage or overlap degree with at least one magnetically conductive body depending on its rotational position. The magnetically conductive element is always arranged outside an area that is surrounded by the coil in every rotation position. The magnetically conductive body is U-shaped, having two limbs which form an intermediate space between them, and with a lateral web connecting them. The magnetically conductive body has bearing points for the shaft formed in an end area of its limbs.
Since the magnetically conductive element is always arranged outside an area surrounded by the coil in every rotation position, it never enters the area surrounded by the coil in any rotation position. Experiments carried out by the applicant have shown that the range of self-inductance of the coil is then advantageously wide. This results in the advantage that the rotation angle sensor is highly accurate and has high resolution.
In this case, the magnetically conductive body is U-shaped, with two limbs which form an intermediate space therebetween, and a lateral web which connects them. The expression “U-shaped” should be understood in its broadest sense, and is also intended to cover all those bodies which have a structure with at least one opening into which the magnetically conductive element can project, that is to say, for example, it also includes C-shaped cross sections. This then allows the magnetically conductive element to project into the intermediate space with a different coverage degree over the limbs, depending on its rotation position.
In the end region of its limbs, the magnetically conductive body has bearing points for the shaft, with the shaft preferably being arranged at right angles to the limbs.
The bearing points for the shaft are, preferably, formed as holes in the limbs.
According to one preferred embodiment, the coil surrounds at least one limb and/or the lateral web of the magnetically conductive body. In this case, the coil can be wound directly on the magnetically conductive body or on a coil former composed of a material that is not magnetically conductive, and is supported by the body.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings.